As you walk through the door of Indiana’s Whirlwind Toys and Hobbies store at 2430 Philadelphia St., it’s hard to imagine what it would have been like to grow up in a world without Lego toys.

For one thing, the store would be a lot emptier, as Lego products line almost the entire west wall of the store from floor to ceiling. The boxes feature an impressive array of cars, planes, bulldozers, pirate ships — even the Millennium Falcon of “Star Wars” fame — that can be built from the tiny pieces inside. Then there are the sets based on popular movies and children’s TV shows such as “The Lord of the Rings,” “Harry Potter” and “Ninjago.” Lego may have outdone itself with the sets based on “The Lego Movie,” released earlier this year. (In other words, there’s a Lego set based on the movie based on Lego sets.)

But if these sets weren’t on the shelves, if they didn’t contain the colorful bricks, plates, doors, tiles and yellow smiling minifigures that rattle around the bottom of toy bins when they’re not part of a skyscraper or a Ferris wheel, then kids in almost every area of the world would miss out on one of the most iconic toys of the past century.

It’s hard to imagine, but the Lego brand actually almost disappeared in the late 1990s and early 2000s when The LEGO Group, based in Denmark, began to flounder as company executives ventured into new products, including a failed television show, that veered too far from the design. Lego sets became so complex that they didn’t offer the chance to build and create original structures, and supply costs for these intricate sets skyrocketed while interest in them faded.

Luckily for The LEGO Group — and people who have loved building with Lego bricks for generations — they turned it around. The company reined in their innovative designers, forcing them to compete against each other instead of green-lighting any idea that made it onto the drawing board. And LEGO executives helped to relaunch the brand and offer something kids actually wanted to play with by having designers work with the noncreative people in the company, according to a 2010 BusinessWeek article.

In other words, they returned to their roots and worked on making and marketing sets that were more recognizably from the Lego brand.

When it became clear a few years ago that the turnaround would last, Whirlwind Toys and Hobbies starting stocking Lego sets and selling them online through its eBay store, and they’ve remained popular ever since.

“They’re a pretty decent seller, so we’ve kept them around,” said Seth Diehl, the store manager. “It’s one of our most popular sections in the store.”

Since they began stocking them about four years ago, Whirlwind Toys has boasted the best selection of Lego sets in the Indiana area, Diehl said, far outstripping what’s available at big box stores.

In addition to their eBay store that sends Lego products “all over the world,” they sell sets that have been retired for years as well as sets that aren’t available in the toy sections of retailers such as Walmart and Kmart.

There’s just something about the Lego brand that resonates with consumers, Diehl said. Just as many of us refer to a facial tissue as Kleenex, consumers associate small plastic building blocks with the Lego brand so much that competitor brands, such as Cobi, just don’t sell as well at Whirlwind Toys.

Even though Cobi and Lego components are compatible with each other, “it’s just not as popular as Lego,” Diehl said.

Part of that may be the name recognition factor, since Lego brand blocks have been available in the United States since 1961. They’ve remained popular among those who grew up at that time and are still a childhood favorite.

“It’s a mix,” Diehl said of his clientele. “Obviously there are a ton of kids, but very often we have adults — big kids — buying them, too,” he said.

Among grownups, the “Star Wars” sets are by far the most popular. With the sets available at Whirlwind Toys, enthusiasts can build the Millennium Falcon spaceship and other spacecraft from the movies, as well as some of the sets from classic battle scenes. Lego even makes minifigures resembling characters such as Darth Vader and Yoda that can hold tiny light sabers.

These sets and even the non-Lego “Star Wars” toys are popular with kids and adults. Diehl is no exception to this trend; the “Star Wars” sets are some of his personal favorites.

“At least once a day, we’ll get someone who comes in and points at something from ‘Star Wars’ like, ‘Oh, I had one of those when I was a kid,’” Diehl said.

Other popular sets include the Lego CITY sets, which feature more realistic vehicles, and the licensed themes from movies and television shows. The more complicated the construction process, Diehl said, the more likely adults are to enjoy a set instead of younger children.

New to the shelves this year are the sets from “The Lego Movie,” which was released in February and earned entirely positive reviews, not to mention a worldwide box office total of $468 million. Diehl also said he’ll be stocking train sets that run on real motors later this month.

Even though many of its products are bulldozers, firetrucks and spaceships, Lego sets are not just popular with boys. Diehl said girls are just as likely to purchase Lego sets, and there are some aimed specifically at them, such as the pink Lego Friends varieties. Lego also recently launched a line of female scientist minifigures, adding to the 1,200 different minifigures created between 1975 and 2010, according to The Complete LEGO Figure Catalog.

The time spent imagining, building and learning is just as important as the finished product.

“We’ve got a ton of dads who come in and build things with their kids,” Diehl said.

Lego bricks, minifigures and other building elements must be precisely designed and manufactured to ensure they’ll be compatible with the other 400 billion pieces already in existence. They also have to be durable for many years and fun to play with. So it’s no surprise that the company’s focus on creativity, engineering and mathematics hasn’t stayed behind the scenes.

Parents and educators looking for ways to help children improve their imaginative and technical chops have increasingly turned to Lego products.

The LEGO Group launched Lego Education 30 years ago as a worldwide education initiative providing educational sets, activity packs and resources for teachers looking to incorporate Lego products in their curricula.

But until recently, there have been few community-minded educational programs using the Lego products.

Tiffany Bacha grew up in the Armagh area and is the owner of the Johnstown-Indiana branch of Snapology, a company in 17 locations around the country that offers robotics, engineering, animation and theme-based programs that use Lego products.

She opened a Snapology office in Indiana in June because she “thought it would be a good opportunity to have this type of program,” she said. “It’s really good enrichment, good STEM-based education, and it’s Legos. Everybody loves Legos.”

Snapology offered a Lego camp for kids 5 to 12 years old at Mack Park’s pavilion during the last week of July. During the week, Bacha and her team worked with 60 kids on two separate areas: building robots and Minecraft, a popular Lego-style computer game. Snapology provided all the materials, supplies and expertise, including local certified teachers.

Campers learned “how to build a stronger robot, make a more agile robot by adjusting gears and changing the center of gravity,” Bacha said. “So it’s basic engineering concepts that we’re applying.”

They also got to create Minecraft worlds and upload them into the game.

But campers don’t have to be Lego enthusiasts to benefit from the program, which is comprised of three lessons each day and a tournament for campers in the robotics program.

“Some kids are very, very much into it and have all the sets, but these programs apply to all kids,” she said.